Cuthona? from East Timor is Antonietta

April 11, 2006
From: Jun Imamoto

Concerning message #16175:

Dear Bill,

Brian Francisco's sea slug reminds me of Antonietta janthina. Is the genus
Antonietta, still appropriate for this species? This photo confirms Baba & Hamatani's mention (1977) that it feeds on Hydractinia epiconcha.

Locality: Osezaki, Izu Peninsula, Suruga bay, 3 m, Japan, Pacific Ocean, 30 April 2002, on  Hydractinia epiconcha. Length: 10 mm. Photographer: Jun Imamoto.

Best wishes,
Jun Imamoto

Imamoto, J., 2006 (Apr 11) Cuthona? from East Timor is Antonietta. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Jun,
I think you are right. The basic colours are the same and the rhinophores, with a paler band about midway down are identical. I think it is the first record outside of Japan.

This is a spectacular photo. I wouldn't be surprised if all the eggs have been produced by these two animals. With such a plentiful supply of food all they need to do is eat and breed. Are they photographed on a rock or is it a large shell? Baba & Hamatani's specimen was feeding on this hydroid growing on  a shell and the name 'epiconcha' suggests it lives on shells. I just wondered whether it was like the European Hydractinia echinata, which is often found on shells, but on rocks as well.

Concerning your question about whether the genus is correct. Baba & Hamatani were not sure if this was the appropriate genus in which to place their species, but I know of no later studies suggesting an alternative. Thanks for this new addition to the Forum

Best wishes,
Bill Rudman

Rudman, W.B., 2006 (Apr 11). Comment on Cuthona? from East Timor is Antonietta by Jun Imamoto. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Related messages

  1. Re: Unknown aeolid is Antonietta janthina
    From: Richard Swann, April 18, 2008
  2. Unknown aeolid from Borneo
    From: Richard Swann, April 17, 2008
  3. Re: Cuthona? from East Timor is Antonietta
    From: Jun Imamoto, April 13, 2006
  4. Another Antonietta janthina from Japan
    From: Jun Imamoto, April 11, 2006
  5. Cuthona? from East Timor
    From: Brian Francisco, April 5, 2006

Show factsheet and all related messages